Motor amperes

[jburgess]

I have an air unit fan motor that has a name plate amp rating of 10.8 amps @ 480v 3-ph. amp clamp reading are 10.5-10.5-12.8. I'm not sure why there is such an unbalance. Motor is virtually new and is part of the air unit. Any suggestions?

 

[stek492]

Re: Motor amperes

You might try a parallel rotation (t1 to t2 t2 to?t3 t3 to?t1). This wont change motor rotation but sometimes it helps get the amp draw closer.

 

[W6SJK]

Re: Motor amperes

What are the Voltage readings?

 

[hurk27]

Re: Motor amperes

If possable try to look at the load side of the contactor for the fan motor. You might be suprised to find a single phase 120 volt load on it. It also could be tapped anywhere between the contactor and the motor.

 

[friebel]

Re: Motor amperes

One suggestion that I might add for the unbalanced readings on the three-phase amperes of a motor.
I would check the readings of the motor windings with a good ohmmeter. There have been times, when a motor winder has inadvertenly wound the motor with not the same number of turns in each phase of the motor windings, hence, that will give you an unbalanced reading of amperes in the three phases.

 

[oliver100]

Re: Motor amperes

I would check the readings of the motor windings with a good ohmmeter.

Good idea.

I would add that a Z value check is more indicative. Autotransformer or any low voltage transformer, voltmeter and ampmeter would do the job.